1. Epithelial Tissue

2. Key Terms Histology: the study of tissues. Tissues:
Simply groups of similar cells that work together performing the same task
Greatest form of teamwork in the body

3. Where are tissues found?
With few exceptions, organs are composed of four basic tissue types:
– Epithelial Tissue
– Connective Tissue
– Muscular Tissue
– Nervous Tissue

4. Why Study Histology?
Knowing the difference between normal and abnormal tissue is the first step in diagnosis and treatment of patients.

5. * made of all four tissue types
Skin, our largest organ
* made of all four tissue types

6. Epithelial Tissue Makes up 3% of your body weight They don’t move
They don’t send messages
Their cells are all touching one another
Of all tissues, they are the most widely varied in structure and function

7. Locations of Epithelial Tissues
Covers the body (epidermis)
Found on the inside of hollow organs and the outside of all organs
Found above a connective tissue layer (epi = above)
Lines the cavities, tubes, ducts, and blood vessels inside the body

8. Epithelial Anatomy
Apical surface – upper surface that is free or exposed to the “exterior”
Basal surface – attached surface (below)
Microvilli – small fingerlike extensions that increase the surface area allowing for more work to be done

9. Functions of Epithelial Tissue
Protects from physical & chemical injury
Protects against microbial infection
Contains nerve endings which respond to stimuli
Filters, secretes & reabsorbs materials
Secretes fluids to lubricate joints

10. Three Basic Shapes
Squamous – like scales, or pancakes (“being squashed like a pancake”)
Cuboidal – looks like cubes
Columnar – longer and look like columns

11. Cell Organization
Simple – single layer of cells; typically found where absorption and filtration occur or a single layer of epithelial is needed
simple squamous
simple cuboidal
simple columnar
Stratified – layers of cells; common in areas where protection is needed like the skin
stratified squamous
stratified cuboidal
stratified columnar

12. Two Types of Stratified Columnar
Ciliated
Unciliated
cilia
No cilia

13. Squamous Epithelium Simple – one cell thick
Forms solid layer of cells which line blood vessels, body cavities and covers organs in body cavities
Stratified – multiple layers
Forms epidermis

14. Cuboidal Epithelium Simple – one cell thick Roughly cube shaped
Cuboid Cells
Simple – one cell thick
Roughly cube shaped
Duct
Line ducts in kidneys where re-absorption and secretion activities take place.
Cuboid Cells
Duct

15. Columnar Epithelium Simple – one cell thick
Column shaped (long and narrow)
Lines digestive tract where re-absorption & secretion occurs.

16. Confusing Epithelial Tissue
Transitional Epithelium – stratified tissue that can’t make up its mind as to whether it is squamous or cuboidal
Shape of cells depends upon the amount of stretching (ex: bladder)

17. Confusing Epithelial Tissue Continued…
“Pseudostratified Columnar Epithelium”
Looks like it has more than one layer because of the position of the nucleus
Nuclei are positioned at differing levels
Cells narrow in the area without the nucleus

18. Epithelial Tissue in Review…

19. Types of Epithelial Membranes
Mucous or mucosa– lining of tubes; moistens and protects from enzymes (stomach, trachea, and vagina)
Serous or serosa – outside of organs; lubricates (all thoracic, abdominal and pelvic organs)
Cutaneous or skin – body surface; protection
Synovial – synovial joints; lines and protects synovial cavities (elbow, knee, hip, etc.)

20. Synovial Membranes
Some joints are surrounded by a membrane (synovium) that produces a thick, synovial fluid. This fluid nourish the cartilage and keeps it slippery.
Knee Joint

21. Mucosa Membranes
Mucus-secreting membrane that lines all body cavities or passages that come in contact with the outside of the body. Membranes are involved in absorption and secretion.
Fungus

22. Serous Membranes
Serous membranes line body cavities that do not open directly to the outside, and they cover the organs located in those cavities. Fluid lubricates the membrane and reduces friction and abrasion when organs move against each other.
Canine Reproductive Organs

23. Cutaneous Membranes
Cutaneous membranes of the skin cover the surface of the body. They consist of stratified squamous epithelium and the underlying connective tissues. Cutaneous membranes are thick, relatively waterproof, and dry.
Skin Cancer